Right click your desktop and create a new text file. Rename that text file to Connection.udf. Double click this file to run it and test your database connection. Once you have all the settings the way you want, close the program. You can now open the UDF file in notepad and you have a proper connection string.

The other thing is to make sure that it allows remote connections. Not sure if SQL Express has this but look for the SQL Server Surface Area Configuration tool and look under DB Engine and then Remote Connections. Check off Using both TCP/IP and named pipes.